Naw it wasnt ever a cat forum.
The main site has always been a depository for ADSL related stuff.
Some time around 2005/2006 I upgraded from shared hosting to a business package that had gave me a lot more flexibility about what I could do and I set up the forums. For 2 reasons: 1) I was getting a heck of a lot of emails asking if I could help re linestats and other queiries relating to content on the main site. 2) A computer related forum that I used to visit and post a lot on was having a lot of server related problems. So it gave somewhere for the regs from CA to post.
I originally used phpbb, but swapped to SMF for security reasons, so some of the earliest posts are no longer available.. I think this is probably one of the earlier ones that still remains -
link.
I honestly dont know how the cat AV thing started. I've used the same AV for years which is one of my cats as a kitten. Zac (the one in my av) died unexpectedly many years ago and I've still never bothered to change it.